I think it depends tbh. If they were going to a particular event (family do, festival involving a special interest of the child, contest or performance of something they are good at, event of lifetime significance - ie a trip to see Rome or a lecture by a prominent person or tour of parliament with the local MP) then I'd have them out of school like a shot, and woe betide any school that thinks they know what is best for my child's education better than me.
But not to get a cheaper holiday in a tourist resort. Call me a snob, but I don't personally see saving money on something non essential as worth the fight.
But then I am the kind of parent that has my under 5 DCs in museums and doing projects and puzzles in holidays anyway. Plus I really want to HE but can't, and would grab flexi schooling with both hands if ever possible. Plus I love a good dispute when I know I am right. Plus I hardly learned anything in lessons till I got to college anyway for various reasons, and in fact learned more when I was able to go home or to a room to study. So I am pretty biased.
Still, I didn't learn anything (apart from that insects are bigger in hot countries) or get any benefit on a family trip to Corfu when I was 14 and in fact refused to go on any more and stayed at home instead reading books and drinking vodka from the next year onwards. So, again, I am biased.
So, my conclusion is - yes to term time holidays for date critical and important events (ie it would be impossible to do at another time) but no for simply saving money on luxury trips.